Floating piston motors



1959 J- H. JARRET ETAL 2,914,046

FLOATING PISTON MOTORS Filed March 31', 1958 mm mv w W W Z. r W J H 5 W 7 n J Jean Marie 54 757? /a/4 Z A fro/ewe? United StatesPatent O FLOATING PISTON MOTORS Jacques Henri Jarret, Le Vesinet, and Jean Marie 'Baptiste Jarret, Saint-Cloud, France Application March 31, 1958, Serial No. 725,293

Claims priority, application France April 1, 1957 Claims. (Cl.-123'46) This invention relates to floating piston motors. In its most usual form, such a motor can be described as comprising a single cylinder chamber in which a pair of conjugate pistons are slidable in opposite symmetrical relation. The pistons are propelled away from each other on their outward stroke by the expansion of combustible mixture which isintroduced into a combustion space between the two pistons, and are propelled towards each other on their inward stroke by resilient restoring means which are adapted to store energy during the outward stroke of the piston and to yield up the stored energy during the inward stroke. The restoring means may comprise ordinary spring means, or air damper means. The pistons in this type of motor are, generally speaking, basically free from any connecting rods, links, crank means, and the like, and may be directly connected to suitable load means, the character of which will depend on the particular use to which the motor is put.

One object of this invention is to provide improved resilient restoring means for propelling a piston in a floating-engine motor back on its inward stroke.

Another object lies in the provision of improved synchronizing means between pistons of a floating-piston engine.

Generally speaking, it has been generally recognized that some suitable means are necessary in order to maintain proper synchronism between the reciprocation of the two conjugate pistons and prevent them from getting out of phase or out of step, since departures from an accurately synchronized condition are conducive to a sharp drop in efliciency. Heretofore-such synchronizing means have usually been provided in the form of mechanical linkages symmetrically coupled to the pistons and coupled together. Such linkages are complicatcd and detract from a basic advantage of floatingpiston engines over conventional combustion engines, i.e. the lack of any mechanical linkages therein. An object of this invention therefore is to eliminate such synchronizing linkages.

In floating-piston engines the fuel is generally supplied, to the cylinder by injector means. Moreover, pressure lubrication means are generally utilized at least in part in connection with such'engines and the loads driven thereby. Objects of this invention are to make eflicient use of the fuel injector means and pressure lubrication in floating piston engines, in furthering the attainment of the objects specified hereinabove.

Further objects of the invention will appear as the disclosure proceeds.

In one aspect of this invention, there is provided a floating-piston motor comprising a cylinder and at least one motor piston displaceable therein, fuel injection and combustion means in said cylinder for driving said pis' ton in one direction under the effect of expansion of fuel combustion gases, and 'fluid-pressure'means adapted to store energy during displacementof said piston in said one direction and thereafter to yield up said energy to drive the piston back in the opposite direction, characterized in that said fluid pressure means comprises an auxiliary cylinder-and-piston means associated with said piston and a body of liquid within said auxiliary means adapted to be compressed to a high degree of pressure during the displacement of said motor piston in said one direction. The degree of compression to which the body of liquid is subjected is in a general range of from kg./sq. cm. to 5,000 kg./sq. cm., and preferably in the range of from 1,000 kg./sq. cm. to 2,500 kg./sq. cm.

It is well-known that liquids, while considerably less compressible than gases, still are compressible. Thus a typical liquid fuel such as gas oil may possess a compressibility on the order of 65.10- per kg./sq. cm. This means thata body of such fuel when subjected to a pressure of 1,000 kg./sq. cm. will sustain a reduction in volume of about 6.5%. By the use of liquid rather than gas as the compressible medium, therefore, the invention is able to achieve a great saving in the volume of fluid required and the space of the resilient restoring means.

In one embodiment of the invention, each piston of a dual-piston floating-piston engine has an auxiliary piston rigidly connected coaxially with it on the side of it remote from the opposite or conjugate motor piston, and the auxiliary pistons are slidable in related auxiliary cylinder chambers supported from the outer ends of the motor cylinder. As the piston assemblies are driven outwards by the expansion force of the combustion gases the auxiliary pistons act to compress bodies of liquid enclosed in,the respective auxiliary cylinder chambers, so as to store up the kinetic energy of the pistons as bydrostatic pressure energy therein, and this pressure en ergy is then given up as kinetic energy again to propel the two piston assemblies on their inward stroke.

According to an improved feature, the auxiliary chamber may be formed with more than one compartment, which are adapted to be sealed off in succession as the auxiliary piston advances through said compartments in the outward stroke, so as to reduce the amount of liquid subjected to volume variation by the auxiliary piston and thereby increase the unit elastic reaction force developed by the liquid (or variation in elastic reaction per unit length).

In a motor according to the invention wherein hydraulic pressure is used especially for the fuel pumping and injecting system, while a separate system may be used for the purpose, according to one advantageous feature of the invention such system is combined into a unitary whole with the piston-restoring liquid compression system described above. For such purpose provision is made for using the engine fuel as the liquid compressed in the auxiliary compression chambers; and a fluid connecting means is provided between said auxiliary chamber or chambers and the fuel injection system.

According to an alternative form of embodiment, lubricant is used as the liquid compressed in the auxiliary compression chamber or chambers, and connecting means are provided from the latter to a pressure lubrication system for the motor.

According to another feature, synchronization between the reciprocation of the two conjugate pistons of a floating piston engine is achieved by providing at least one balancing conduit interconnecting the auxiliary compres-. sion chambers that are provided in association with the respective motor pistons according to the main feature described above. I i i An exemplary embodiment of the invention will now be described for purposes of illustration but not of limitation with reference to the accompanying drawing, which is a simplified sectional view of a floating-piston engine jugate pistons 2 and 3 slidable therein. The cylinder 1 is formed with inlet ports 4 and an outlet pipe 5. Each piston is rigidly connected to a structure 67, bodily movable with it, which structure may include conventional guiding and power take-ofl? means, not illustrated herein, positioned in the gaps indicated herein as 6a and 7a.

Secured on the outer end of the structure 6 or 7'is an auxiliary compressor piston 8 or 9 slidable in a sealed metallic enclosure 10 or 11 secured to-the cylinder 1, and filled with a body of liquid adapted to be compressed by the auxiliary piston 8' or 9.

In the specific embodiment of the invention here illustrated, the liquid is formed by the engine fuel. The liquid fuel is supplied from a fuel tank, not shown, by way of lines 12-13. A further pair of lines 14 and 15 provided with check-valves 16 and 17 therein, serve to lead part of the compressed liquid to the fuel injector device 18 which may be conventional, whereby the invention will be seen to provide improved means for supplying fuel under pressure to the injector means of afioating-piston engine. The lines 14 and 15 are connected with the enclosures 10 and 11 at points so positioned in said enclosures that the liquid pressure obtaining at the time where the piston 3 or 9 is in the act of sealing said connection, equals the pressure value required to operate the injector device 18, with due allowance of course for the pressure drop between the injector 18 and the said connections. It is noted moreover that said pressure drop is controllable.

In the exemplary embodiment shown, the sealed enclosure includes, in addition to the main compression chamber 19-20, a secondary compression chamber 21, 22, of annular form, and communicating with the main chamber through ports 23, 24 which are sealed by the piston 8 or 9 as the latter is moving into the body of liquid, i.e. during the outward stroke of the motor pistons 2 and 3. On the ports 23, 24 being sealed, the pressure in the secondary chamber 21 or 24 remains substantially constant, while it continues to increase in the main chambers 19 and 20, and it now increases at a faster rate than what would have occurred had the said ports not been sealed 01f. The result of this arrangement is that an increased elastic resistance is opposed to the outward motion of the piston assembly during the latter stage of the outward stroke. Further, as a result of this arrangement the displacement of the piston assembly will vary but little with variations in engine operating speed which cause corresponding variations in the energy stored in the energy-storage devices.

In accordance with another desirable feature of the invention included in the exemplary embodiment shown, improved synchronizing means are provided between the two conjugate motor pistons, in the form of a balancing line 25 interconnecting the chambers 19 and of the energy storage devices. The presence of this balancing line gives rise to interchange of energy between the two devices, so that balancing forces are set up which prevent the two pistons assemblies from falling out of step (or out of phase). Thus, assuming that one of the movable assemblies tends to lead the other, energy will be transferred from the leading assembly to the lagging side,

shortening the distance travelled by the latter and corre- Power output: 15 HP.

Pulsing frequency: 100 piston cycles per second- Motor cylinder bore: mm.

Piston stroke: 60 mm.

Auxiliary cylinder bore (corresponding to piston 8):

Total volume of an hydraulic compression space 19 2123: 30 cu. cm., of which about 50% in chamber 2123 and 50% in chamber 19.

Useful axial contraction of the liquid body: 24 to 25 mm.

Maximum hydraulic pressure developed, average values: in

compartment 21: about 800 kg./sq. cm. in compartment19: about 1,600 kg./sq. cm.

A floating piston engine constructed in accordance with the teachings ofthis invention has a number of important advantages, in that it simplifies the compression means previously provided and permits reduction in the weight of the movable piston assemblies and corresponding increase in the power-to-mass ratio of the engines.

This results mainly from the fact that the volume of the hydraulic compression chamber required is, as an order of magnitude, one thousand times smaller than the volume of the air cushion that has to be used in a pneumatic compression chamber for a motor of given power rating.

Among the various modifications and variations that may be conceived by those familiar with the art on the basis of the teachings given herein, the following may be more specifically mentioned:

More than one liquid compression unit similar to those here shown may be used in connection with each motor piston assembly.

A liquid compression unit according to the invention may be combined with a conventional air compression unit.

An engine lubricating system may be provided, wherein at least one of the liquid compression devices of the invention operates as a pumping device for the liquid lubricant.

Adjusting means may be associated with the sealed enclosure for increasing or decreasing the volume of liquid compressed and thereby modifying the length of stroke of the piston assemblies.

What we claim is:

1. In a combustion engine of the type described, a cylinder, a piston reciprocable therein, means for supplying combustible mixture into said cylinder and firing said mixture to drive said piston in one direction, means defining a capacity enclosing a body of liquid, and compressor means connected with said piston and operating to compress said body of liquid during movement of the piston in said one direction, for driving the piston back in the opposite direction.

2. In a combustion engine of the type described, a cylinder, a piston reciprocable therein, means for supplying combustible mixture into the cylinder and for firing said mixture to drive the piston in one direction, an auxiliary cylinder outside said first cylinder, an auxiliary piston rigidly connected with said first piston and slidable in said auxiliary cylinder, and a body of liquid in said auxiliary cylinder adapted to be compressed by said first piston during movement thereof in said one direction, so as to store energy therein and thereafter give back said energy to said first piston to drive it back in the opposite direction.

3. In a combustion engine of the type described, a cylinder, a piston reciprocable therein, fuel injection and firing means for creating an expansion force in said cylinder to drive the piston in one direction, an auxiliary cylinder outside said first cylinder and coaxial therewith,

an auxiliary piston rigidly connected with said first piston and slidable in said auxiliary cylinder, and a body of liquidin said auxiliary piston, adapted to be compressed by said auxiliary piston during movement in said one direction, the relative dimensioning being such that said liquid is compressed to a pressure within a range of from about to about 5,000 kg./sq. cm.

4. The. combination claimed in claim 3, wherein said.

pressure is within a range of from 1,000 to 2,500 kg./ sq. cm.

5. The combination claimed in claim 2, wherein said auxiliary cylinder is formed to define more than one compartment therein, said compartments being adapted to be sealed ofi in succession by said auxiliary piston during movement in said one direction.

6. In a combustion engine of the type described, a cylinder, at least one piston reciprocable therein, liquid fuel injector means for supplying fuel-air mixture into said cylinder and for firing said mixture to drive said piston in one direction, means defining an auxiliary cylinder, a source of liquid fuel, conduit means connecting said source with said injector means and with said auxiliary cylinder whereby said auxiliary cylinder is filled with liquid fuel, and an auxiliary piston connected with said first piston and cooperating with said auxiliary cylinder for compressing said liquid fuel therein on movement of said first piston in said one direction.

7. In a combustion engine of the type described, a cylinder, at least one piston reciprocable therein, means for supplying a combustible mixture to said cylinder and for firing said mixture to drive said piston in one direction, means defining an auxiliary cylinder, a pressure lubrication system for said engine including a source of liquid lubricant, conduit means connecting said source with said auxiliary cylinder to fill the latter with said lubricant, and a compressor member connected with said piston and cooperating with said auxiliary cylinder means to compress said lubricant therein on movement of said piston in said one direction to generate a force for thereafter driving back the piston in the opposite direction.

8. In a combustion engine of the type described, a cylinder, a pair of conjugate pistons reciprocable therein, means for supplying a combustible mixture to said cylinder between said pistons and for firing said mixture to create a force driving both said pistons simultaneously outwards, means defining sealed capacities beyond the ends of said cylinder, liquid filling said capacities, compressor members connected for movement with said pistons and cooperating with said respective capacities to compress said liquid therein on outward movement of said pistons, whereby expansion of said liquid will thereafter create a force for driving both said pistons simultaneously inwards again.

9. In a combustion engine of the type described, a cylinder, a pair of conjugate pistons reciprocable therein, means for supplying a combustible mixture to said cylinder between said pistons and for firing said mixture to create a force driving said pistons outwards, means defining sealed capacities beyond the ends of said cylinder, liquid filling said capacities, compressor members connected for movement with said pistons and cooperating with the respective capacities to compress said liquid therein on outward movement of the pistons, whereby expansion of said liquid on completion of said outward movement will create a force for driving both pistons inwards again, and balancing conduit means interconnecting both said capacities.

10. In the motor claimed in claim 2, means for adjusting the volume of said liquid in the auxiliary cylinder to control the displacement of said piston.

References Cited in the file of this patent UNITED STATES PATENTS 2,473,204 Huber June 14, 1949 2,671,435 Spier et al. Mar. 9, 1954 2,815,641 Ramsey et al, Dec. 10, 19 57 

